High intensity wet magnetic separators

ABSTRACT

An improved high intensity wet magnetic separator is described having a horizontal rotor in the form of a heavy disc of highly magnetically permeable material surrounded by an annular member having a series of gaps extending vertically therethrough. Induced pole pieces are mounted in the gaps and a pair of diametrically opposed electromagnets are provided with pole pieces adjacent the rotor. A magnetic field is formed between the pole pieces and the rotor through the gaps where magnetic separation from a slurry takes place.

United States Patent [191 Stone 1 1 HIGH INTENSITY WET MAGNETIC SEPARATORS [76] Inventor: W. .1. Dennis Stone, 253 Westcroft Ave., Beaconsfield, Quebec, Canada 22 Filed: June 26,1972 21 Appl. No.: 266,239

[52] US. Cl 209/223, 209/222, 209/232 [51] Int. Cl. B03c 1/02 [58] Field of Search 209/220, 222, 223, 219, 209/214 [56] References Cited UNITED STATES PATENTS 456,622 7/1891 Lain 209/223 X 805,854 1 H1905 Medburg... 209/220 2,074,085 3/1937 Frantz 209/222 X 3,246,753 4/1966 Laurila... 209/219 3,326,374 6/1967 Jones 209/232 X 3,375,925 4/1968 Carpenter 209/222 X 3,595,386 7/1971 Wl'adel 209/214 X [111 3,830,367 [451 Aug. 20, 1974 FOREIGN PATENTS OR APPLICATIONS 159,108 3/1905 Germany 209/222 252,034 5/1926 Great Britain 209/220 294,321 9/1969 Australia 209/223 1,914,718 10/1970 Germany 209/223 Primary Examiner-Robert Halper Attorney, Agent, or Firm-Christen & Sabol ABSTRACT An improved high intensity wet magnetic separator is described having a horizontal rotor in the form of a heavy disc of highly magnetically permeable material surrounded by an annular member having a series of gaps extending vertically therethrough. Induced pole pieces are mounted in the gaps and a pair of diametrically opposed electromagnets are provided with pole pieces adjacent the rotor. A magnetic field is formed between the pole pieces and the rotor through the gaps where magnetic separation from a slurry takes place.

5 Claims, 9 Drawing Figures PAIENTEDAUGZOIBH 830.367 sum 2 or 3 .9 RETURN YOKE CIRCUIT RETURN COL CIRCUIT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to magnetic separators for separating materials of differing magnetic susceptibility and, more particularly to a high intensity wet magnetic separator capable of separating feebly magnetic materials from non-magnetic materials.

2. Description of the Prior Art Magnetic separation has long been known as a valuable technique in mineral separation and has been particularly useful in the separation of strongly magnetic materials from non-magnetic materials. Although the greatest commercial use of magnetic separators has been found in dry separation processes, recently new types of magnetic separators have been very successfully used under wet conditions.

In the past, magnetic separators have generally been in the form of an axially rotatable drum having disposed interiorly thereof a plurality of fixed magnets. These magnets are normally placed in close proximity to the desired area of the interior surface of the drum so that when magnetic particle-carrying matter is fed against that peripheral portion of the drumoverlying the fixed magnets, the magnetic particles adhere to the drum and are then carried to a discharge position. The non-magnetic material unaffected by the magnetic field normally is permitted to fall under the force of gravity for separate collection. When such equipment is employed for wet separating processes, a slurry or pulp of the material to be separated either is fed to the periphery of the drum in the same manner as dry materials or, the rotating drum may be partially submerged in a liquid slurry.

More recently for wet separation there has been developed the so-called high intensity wet magnetic separator and the most commercially successful of these is the so-called Jones separator. A typical design of the Jones separator is described in Canadian Pat. No. 717,830 issued Sept. 14, 1965. It was of circular design with a series of vertically mounted grooved plates in circular configuration which rotated through alternating magnetic fields. In this manner a magnetic field was introduced in the grooved plate sections as they passed a magnetic pole then reached a point of zero magnetic field between poles of opposite polarity and a high magnetic field at the next magnetic pole. A feed slurry was fed into the grooved plates in the region of a magnetic pole so that the magnetic particles adhered to the plate walls. A water flush was applied to help washaway the non-magnetic materials and then at a point of low or zero magnetic field the magnetic particles were released from the plates with the assistance of high pressure water scouring. The magnetic and nonmagnetic materials were collected in separate launders. Magnetic pole pieces were usually provided on opposite sides of the grooved plate sections and in order to obtain strong magnetic fields, these were usually in the form of electromagnets. Although this system worked quite well, its main deficiency tended to be that of not being able to achieve a sufficient zone of zero magnetism during which all of the magnetic materials could be removed from the plates.

It is, therefore, the object of the present invention to provide an improved design of the basic Jones separator which will provide more effective separation of magnetic materials from non-magnetic materials.

SUMMARY OF THE INVENTION According to the invention a rotary high intensity wet magnetic separator is provided comprising an assembly having a support frame with a vertical shaft rotatably mounted on the frame. The shaft carries a rotor in the form of a heavy disc of highly magnetically permeable material mounted for horizontal rotation and an annular structure of containing a series of vertical gaps surrounding and connected to the disc. Each of these rotor gaps contains a plurality of induced pole pieces and a pair of electromagnets of opposed polarity are mounted in diametrically opposed positions adjacent the rotor. The' electromagnets include pole pieces having edge faces in close proximity to the edge of the rotor whereby a minimum air gap is provided between the pole pieces and the rotor.

Inlet means are provided for feeding a slurry feed to the upper portion of the rotor gaps at the leading edge of the magnetic field produced by each electromagnet. The magnetic particles immediately adhere to the induced pole piece surfaces while the non-magnetic particles pass straight through. Collecting launders are positioned beneath the rotor gaps in these regions to separately collect the non-magnetic particles.

Inlet means are also provided for delivering a first flushing fluid to the upper portion of the rotor gaps before they leave each magnetic field. These are preferably low pressure water washes and they serve to remove non-magnetic material which is trapped by the adhering magnetic particles. Collecting launders are also positioned beneath the rotor gaps in these regions to separately collect a middlings product. This middlings product contains some magnetic particles and can be recycled into the feed slurry.

Other inlet means are provided at the mid-point between the electromagnets where the magnetic field is zero for delivery of a second flushing fluid to the upper portion of the rotor gaps. These are preferably high pressure water jets which assist in removing the magnetic particles from the induced pole piece surfaces. Collecting launders are also positioned beneath the rotor gaps in these regions to separately collect the magnetic products.

DESCRIPTION OF PREFERRED EMBODIMENTS The edge faces of the pole pieces adjacent the rotor are arcuate and, according to a unique feature of this invention, these faces are very wide with each face forming an arc of preferably about 4590 and conforming to the curvature of the rotor. This provides a very substantial zone of high intensity magnetic field in which the initial magnetic separation occurs and the middling wash and removal of middlings product is carried out. The result of this is a very high degree of magnetic particle collection during each cycle.

Surprisingly it has been found that this very simple construction of a pair of diametrically opposed pole pieces with the central heavy rotor disc of highly magnetically permeable material gives exceptionally im' proved overall separation. The reason for this is believed to be that the heavy rotor disc provides a very efficient return magnetic circuit so that at substantially mid-points between the opposed electromagnets of reversed polarity, the circumferential edge of the disc and the adjacent induced pole pieces quickly reach a state of substantially zero magnetism. Because this state of substantially zero magnetism is reached very quickly, the effect is that the circumferential zone of substantially zero magnetism where magnetic particles can be very efficiently removed from the induced pole pieces is very significantly increased in length. This becomes particularly significant for separation of strongly magnetic particles since the extended zone is sufficient for them to become totally de-magnetized and released from the induced pole pieces. Otherwise there is a gradual build-up of strongly magnetic particles which decreases the efficiency of the separator. Of course, it also follows that the same arrangement will quickly return to maximum magnetic field under influence of the electromagnets thereby also providing a maximum zone of high intensity magnetic field. In other words, the system minimizes the intermediate zones of increas ing and decreasing magnetic field which are not beneficial to an efficient separation cycle.

According to a particularly preferred embodiment of the invention each electromagnet is formed with a substantially U-shaped yoke so that the arms of the yoke are vertically spaced. A separate magnetic coil is wound around each yoke arm so that a pair of vertically spaced magnetic pole pieces are provided. A corresponding pair of rotors are then mounted on the vertical shaft so that two separation stages can be provided on the one machine. Separate slurry feed inlets, flushing water inlets and collecting launders can be provided in association with each rotor so that they may operate independently.

The induced pole pieces are preferably in the form of a series of mild steel grooved plates. However, it is also possible to use other forms such as helical rods, cubes, spheres, etc. They are preferably characterized by a number of sharp edges, corners or surfaces causing convergance of the lines of force of the effective magnetic field in which the pieces are disposed. In the case of grooved plates the magnetic flux is concentrated at the tips of the ridges and by correct selection of the plate gap and magnetic field the collection of feebly magnetic particles can be ensured. The space between adjacent peaks is usually in the order of lmm and is preferably about 2.5 mm.

This machine is capable of separating a wide variety of different materials and, for instance, it may be used for making a magnetic concentrate when the magnetic material is the required product, e.g., iron ore, hematite, pyrrhotite, siderite, ilmenite, ores of chromium, manganese, tungsten, zinc, nickel, tantalum/niobium, molybdenum and other feebly magnetic minerals. Alternatively, it can be used for operating by the removal of impurities when the non-magnetic material is the required product, e.g., glass, sand, heptatite, clay, talc, kaolin, baryte, graphite, bauxite, cassiterite, etc. Such impurities include biotite and moscovite, iron-stain particles, garnet, iron silicates, horn blend, termaline, etc. Yet another use is for waste water treatment, e.g., removal of particles from steel mill waste water. Preferably the material being fed to the separator has a particle size of less than 1 mm.

Having generally described the present invention, more detailed illustration is given with reference to the following drawings in which:

FIG. 1 is a side elevation in partial section of the separator;

FIG. 2 is a top plan view in partial section;

FIG. 3 is an end elevation;

FIG. 4 is a sectional view showing details of the rotor and electromagnets;

FIG. 5 is a plan view showing details of the rotor;

FIG. 6 is a perspective view of the rotor;

FIG. 7 is a sectional view showing details of a washing head;

FIG. 8 is a perspective view showing details of a plate box, and

FIG. 9 is a sectional view showing details of a plate box.

As will be seen from FIGS. 1, 2 and 3, the structure is constructed with a very strong main frame with verti cal structural steel beams 10 and horizontal beams 11. Mounted on this frame are a pair of heavy magnet yokes 12 around the arms of which are electromagnetic coils 13. These coils are cooled by way of air cooling units 14.

A rotor shaft 15 is vertically mounted for rotation in heavy roller bearings 17 and a drive unit 16 comprising a worm gearing driven by an electric motor through V- belts is mounted directly to shaft 15.

Mounted at vertical spaced locations on shaft 15 in alignment with yokes 12 are a pair of heavy mild steel discs 18. Around the periphery of these discs 18 are mounted a series of plate boxes 19 containing grooved plates. Above these plates is mounted a launder 20 through which feed slurry is fed into the plate boxes. Directly below the plate boxes are collecting launders 21 which alternatively receive non-magnetic products, middling products and magnetic particles and these are connected to separate outflow pipes 22.

The complete cycle of the machine can best be observed from FIG. 5. This shows the flows through the upper rotor and it will be seen that as the plate boxes 19 come into the influence of the south pole electromagnet, feed slurry is continuously fed in through feed inlet 25. The magnetic particles immediately adhere to the plate surfaces with non-magnetic particles passing straight through. Of course, a certain amount of nonmagnetic material is trapped with the magnetic particles when they adhere to the plates and these are removed by means of a middling wash of low pressure wash water continuously fed in through water inlet 26. Following this the plate boxes depart from the influence of the south pole electromagnet and approaching the mid-point between the south pole and north pole electromagnet they reach a zone of substantially zero magnetism where the magnetic particles release from the plate surfaces. To assist in dislodging the particles, a series of high pressure scouring water sprays 27 operating at up to psi are sprayed through the plate boxes to complete the dislodgment of the particles. Separate collecting launders are provided under each of the feed, middling wash and magnetics wash zones and these launders are all connected to separate discharge pipes so that three separate effluents are collected.

Corresponding feed inlet 25', middling wash 26' and magnetics wash 27' devices are provided in association with the north pole electromagnet and beneath the devices 25 26 and 27' are also provided collecting launders and effluent pipes. These provide a full duplication of the cycle in association with the south pole electromagnet so that two complete separation cycles occur during each full revolution of the rotor.

The plate boxes are shown in greater detail in FIGS. 6 to 9 and it will be seen from FIG. 6 that they have formed with an inner ring 30 adjacent disc 18 out from which project a series of radial side plates 31 of non- Thus, it can be seen that the concentrate obtained was up-graded to 67.9 percent Fe and the recovery was 95.5 percent Fe.

Example 2 magnetic material to which are connected outer plates 5 The same'procedure was used as in Example 1 but for 32. These together make up a series of rectangular veri P of a Superconcemrati- T Stamng tical openings 33. Packed into these rectangular openterm} w a splral concentrate cqmflmmg v 85 percent ings are rows of grooved plates 33 with vertical spaces hemame and 6 percent fi e- It had a grade of 34 therebetween through which the feed material ,i. a g partlck? size 35 i passes. Spacer bars 35 can be provided between the Sh g p i t e odpefiatlon are 8 own In grooved plates for maintaining a proper plate spacing. eet an e note t at two passes were ma The actual space between plates can be varied depend- 1 mg on requirements but typically the space between armg ma em adjacent peaks is 2.5 mm. 1??? e e 1s A completely separate set of Inlet and outlet launders 100 0 65 2 100 0 and pipes are provided for the upper and lower rotors so that the flows through the two rotors are quite indei pendent from each other. However, it will be under- T Separator feed stood that the flows as described above through the upper rotor will be the same for the lower rotor. s e: gg gig Certain commercial uses of the separator of this in- 106 6 64 3 105 2 vention are illustrated by the following examples: 1

H.I.W.M. separator#1 pass Magnetics #1 Wash #1 Non-magnetics #1 Percent Percent Percent Percent Percent Percent Percent Percent Percent wt. Fe Fe dist. wt. Fe Fe dist. wt. Fe Fe dist.

l t I j II.I.W.M. separator-#2 pass Magnetics #2 Wash #2 Non-magnetics #2 Percent Percent; Percent Percent Percent Percent Percent Percent Percent wt. Fe Fe dist. Wt. Fe Fe dist. wt. Fe Fe dist.

l 1 l Superconcentrates 1.0% insolubles) Tailings The concentrate obtained had a grade of 69.1 percent Fe and the recovery was 90.6 percent.

I claim:

l. A high intensity wet magnetic separator comprismg:

Fe. a support frame;

lt was fed as a slurry to the separator and the mida pair of vertically spaced upper and lower rotor andlmgs product was re-cycled nto he feedstreamnular assemblies having discs mounted on a vertitlCUlaI'S 0f the operation are ShOWl'l in the fOllOWll'lg ca], rotatable haft, each said rotor disc having 3, Flow Sheet l: so heavy central disc portion of highly magnetically permeable material surrounded by an annular as- Stertlng materiel l sembly having spaced openings extending vertiaj i ilg g ggg' t cally therethrough, each opening holding a pluralmo 0 39 7 100 0 ity of induced pole pieces to permit passage of particulate material therethrough;

S at f d a pair of diametrically opposed electromagnets of opa posite polarity each having a substantially U- sy i gg shaped yoke forming upper and lower pole pieces n9 6 38 6 109 4 ad acentsaid upper and lower rotor annular assemblies, each said pole piece having an arcuate face 1 .I.W.M. separator Magnetics Middling wash Non-megnetics Percent Percent Percent Percent Percent Percent Percent Percent Percent wt. Fe Fe dist. wt. Fe Fe dist. wt. 0 Fe dist.

55. 8 67. 9 95. 5 12. ti 2!). (i 9. 4 44. 2 4. 0 4. 5

0 L l Concentrate l o o Tunings of about 45 to the upper rotor forming one return circuit and the lower rotor forming the other return circuit; separate inlet means associated with each rotor for feeding a slurry feed to the upper ends of said rotor openings at the leading edge of the magnetic field produced by each electromagnet pole piece;

separate inlet means for delivering a first flushing fluid to the upper ends of said rotor openings before leaving each said magnetic field;

separate inlet means associated with each rotor for delivering a second flushing fluid to the upper ends of said rotor openings at the mid-points between said electromagnet pole pieces and separate collecting means disposed below said rotor openings at points below each of said feed and flushing inlet means.

8 2. A magnetic separator according to claim 1 wherein each heavy rotor disc is fabricated from mild steel.

3. A magnetic separator according to claim 1 wherein said rotor openings are in the form of rectangular passages separated by radial dividers.

4. A magnetic separator according to claim 3 wherein said rectangular passages contain a series of vertical, spaced, parallel grooved plates of highly magnetically permeable material.

5. A magnetic separator according to claim 3 wherein a pair of vertical, circular walls extend upwardly on each side of said rectangular passage tops, forming an annular launder for directing feed slurry and flushing fluids into the passages. 

1. A high intensity wet magnetic separator comprising: a support frame; a pair of vertically spaced upper and lower rotor annular assemblies having discs mounted on a vertical, rotatable shaft, each said rotor disc having a heavy central disc portion of highly magnetically permeable material surrounded by an annular assembly having spaced openings extending vertically therethrough, each opening holding a plurality of induced pole pieces to permit passage of particulate material therethrough; a pair of diametrically opposed electromagnets of opposite polarity each having a substantially U-shaped yoke forming upper and lower pole pieces adjacent said upper and lower rotor annular assemblies, each said pole piece having an arcuate face of about 45* to 90*, the upper rotor forming one return circuit and the lower rotor forming the other return circuit; separate inlet means associated with each rotor for feeding a slurry feed to the upper ends of said rotor openings at the leading edge of the magnetic field produced by each electromagnet pole piece; separate inlet means for delivering a first flushing fluid to the upper ends of said rotor openings before leaving each said magnetic field; separate inlet means associated with each rotor for delivering a second flushing fluid to the upper ends of said rotor openings at the mid-points between said electromagnet pole pieces and separate collecting means disposed below said rotor openings at points below each of said feed and flushing inlet means.
 2. A magnetic separator according to claim 1 wherein each heavy rotor disc is fabricated from mild steel.
 3. A magnetic separator according to claim 1 wherein said rotor openings are in the form of rectangular passages separated by radial dividers.
 4. A magnetic separator according to claim 3 wherein said rectangular passages contain a series of vertical, spaced, parallel grooved plates of highly magnetically permeable material.
 5. A magnetic separator according to claim 3 wherein a pair of vertical, circular walls extend upwardly on each side of said rectangular passage tops, forming an annular launder for directing feed slurry and flushing fluids into the passages. 